Airflow characteristics in a baboon nasal passage cast

Airflow patterns in the nasal passages influence the distribution of air-pollutant-induced lesions in the airway mucosa. Little is known about airflow characteristics of the complex nasopharyngeal airway of humans and experimental animals. Airflow characteristics in the nasopharyngeal airways of an adult male baboon (13.9 kg body wt) were investigated with thermistor probes and the findings compared with flow visualization, using a cinephotographic technique. A clear, acrylic, hollow cast of a baboon nose was made, and thermistor probes were inserted to record air velocity in the cast lumen using a wind tunnel to propel air through the cast. An identical cast was studied by passing water through the cast, with pulses of dye to reveal flow, and cinephotography was used for determination of flow velocities and flow patterns. Flow rates adjusted on the basis of a Reynolds conversion showed good correlations between the two methods, whereas cinephotography revealed areas of turbulence and vortex-like flow not detected by thermistor probes. These results suggest that water flow may provide useful information in complex airways where airflow cannot be determined by other methods.